1. Field of the Invention
The present invention relates to a stitched write head with a staircase defined second pole piece (P2) throat height and, more particularly, to such a write head and method of making wherein a first component of P2 can be fabricated on a planar surface for defining the throat height and a second component of P2 can be fabricated on a planar surface including the first component with a track width so that the second component can be employed as a mask for ion milling the first component with the track width.
2. Description of the Related Art
The heart of a computer is a magnetic disk drive which includes a rotating magnetic disk, a slider that has a magnetic head assembly which includes write and read heads, a suspension arm. When the disk is not rotating the actuator arm parks the suspension arm on a ramp. When the disk rotates and the slider is positioned by the arm above the disk air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the actuator arm swings the suspension arm to place the write and read heads over selected circular tracks on the rotating disk where signal fields are written and read by the write and read heads. The write and read heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
A write head typically employs ferromagnetic first and second pole pieces which are capable of carrying flux signals for the purpose of writing signal fields into a track on a magnetic medium, such as a rotating magnetic disk. Each of the first and second pole pieces has a yoke region which is located between a pole tip region and a back gap region. The pole tip region is located at the ABS and the back gap region is spaced from the pole tip region at a recessed location within the write head. At least one coil layer is embedded in an insulation stack which is located between the first and second pole pieces in the yoke region. A nonmagnetic write gap layer is located between the pole tips of the first and second pole pieces and the first and second pole pieces are magnetically connected at the back gap. Processing circuitry digitally energizes the write coil which induces flux into the first and second pole pieces so that flux signals bridge across the write gap at the ABS to write the aforementioned signal field or magnetized bits into the track of the rotating disk.
A write head is typically rated by its areal density which is a product of its linear bit density and its track width density. The linear bit density is the number of bits which can be written per linear inch along the track of a rotating magnetic disk and the track width density is the number of tracks that can be written per inch along a radius of the rotating magnetic disk. The linear bit density is quantified as bits per inch (BPI) and the track width density is quantified as tracks per inch (TPI). The linear bit density depends upon the thickness of the write gap layer, pole materials, throat height, flight height and media characteristics. The track width density is directly dependent upon the width of the second pole tip at the ABS. Efforts over the years to increase the areal density has resulted in increased computer storage capacities over the past few decades.
The throat height of a write head plays a key role in obtaining a desirable BPI. The throat height of a write head is the distance from the ABS to a recessed location within the head where the first and second pole pieces first commence to separate after the ABS. The recessed location is referred to in the art as the zero throat height (ZTH). As write gap and flight height is decreased, the short throat height length is required to render high efficiencies with sufficient write field and field gradient for linear bit definition. The tolerance control of throat height variation is critical for a short throat height writer to ensure consistent writer performance and device yield. In order to achieve superior tolerance control, a planar surface is greatly preferred for the photolithographic process which defines zero throat position.
Another aspect in the construction of high areal density write heads is the track width density of the head. The track width density depends upon the distance between the first and second side walls of the second pole piece. Frame plating is typically employed to fabricate the second pole tip which is defined by a photolithographic pattern prior to plating. When the second pole tip is a separate component of the second pole piece, which is fabricated before the fabrication of the yoke portion of the second pole piece, the first and second side surfaces of the second pole tip can be well-defined.
A typical design is to employ a first pole piece (P1) pedestal for defining the throat height. In order to achieve required magnetic performance, however, the throat height of the pedestal must be long (1.0 μm–2 μm) so that the P1 pedestal is not over-saturated causing a low write efficiency for a writer with narrow write gap and track width. Another scheme for achieving the throat height is to fabricate a first component of the second pole piece over a resist bump. The resist bump elevates the first component so as to define the throat height. Unfortunately, the resist bump creates a non-planar structure near the ABS which makes it difficult to fabricate a precise track width during the photo/trim patterning process. Accordingly, there is a strong-felt need to fabricate a write head with a precise zero throat height so as to optimize the BTI and the TPI as well as fabricating a precise and narrow track width so as to maximize the TPI.